Lithography process is widely used in the formation of Integrated circuits. It is one of the most important processes in the semiconductor fabrication. That is because the formation of the integrated circuits require that precisely controlled quantities of dopants be implanted into tiny regions of a layer or a wafer. Further, the sizes of various circuit elements, from transistor bases to lead widths, must be determined and their exact position on the chip established.
Typically, the photoresist is applied as a thin film to a wafer or an underlying layer, and then exposed through a mask (or reticle in step-and repeat projection system). The mask contains clear and opaque features that define the pattern to be created in the photoresist layer. The regions in the photoresist exposes to the light are made either soluble or insoluble in a specific solvent known as a development. Following development, the regions of the underlying layer no longer covered by the photoresist are removed by etching, thereby replicating the mask pattern in that underlying layer. In general, photoresist has several components. For example, the resin is one of the components. A sensitizer is very photosensitive. Since the exposure process requires changes in molecular bonding, substantial photo energy such as ultraviolet light is required. In general, photoresist is used to serve an etching mask or an ion implantation mask. The pattern in the photoresist is generated when the substrate undergoes the step of development. The residual photoresist is left on the underlying layer to prevent a portion of the underlying layer from etching or to serve a mask for implantation.
However, one of the problems related to the photoresist supplying system is the poor coating of the photoresist. It is due to bubbles trapped in the photoresist supplying system. The photoresist supplying system force the photoresist to spray on the wafer via gas. The residual gas may be trapped in the photoresist supplying system. In addition, the gas may be come from the procedure of filter replacement. The gas may get into the filter while the filter is dismantled from the system for replacement. Thus, the bubbles are generated by this procedure. Therefore, the control of the photoresist volume becomes difficult due to the bubbles that are trapped in the pipe, the filter of the system. While the bubbles are dispensed on the wafer, they will cause poor coating on the wafer. Thus, what is required is a photoresist supplying system that will eliminate the residual bubble in the system.